The present invention relates to an air bearing slider for use in a data storage device such as a disc drive. More particularly, it relates to an air bearing slider which allows for control of pressurization and suction force formation.
Air bearing sliders have been extensively used in magnetic disc drives to appropriately position a transducing head above a rotating disc. In a disc drive, each transducer xe2x80x9cfliesxe2x80x9d just a few nanometers above a rotating disc surface. The transducer is mounted in a slider assembly which has a contoured surface which faces the disc surface. An air bearing force is produced by pressurization of the air as it flows between the disc and slider and is a consequence of the slider contour and relative motion of the two surfaces. The air force prevents unintentional contact between the transducer and the disc. The air bearing also provides a very narrow clearance between the slider transducer and the rotating disc. This allows a high density of magnetic data to be transferred and reduces wear and damage.
In most high capacity storage applications, when the disc is at rest, the air bearing slider is in contact with the disc. During operation, the disc rotates at high speeds, which generates a wind of air immediately adjacent to the flat surface of the disc. This wind acts upon a lower air bearing surface of the slider and generates a lift force directing the slider away from the disc and against a load beam causing the slider to fly at an ultra-low height above the disc.
In negative pressure sliders, the wind also acts upon a portion of the air bearing surface of the slider to generate a suction force. The suction force counteracts the lift force by pulling the slider back toward the surface of the disc. A slider is typically mounted on a gimbal and load beam assembly which biases the slider toward the rotating disc, providing a pre-load force opposite to the lift force acting on the air bearing surface of the slider. For the slider to maintain the ultralow flying height above the surface of the disc, the lift force must be balanced with the pre-load and suction forces.
As disc storage systems are designed for greater and greater storage capacities, the density of concentric data tracks on discs is increasing (that is, the size of data tracks and radial spacing between data tracks is decreasing), requiring that the air bearing gap between the transducing head carried by the slider and the rotating disc be reduced. One aspect of achieving higher data storage densities in discs is operating the air bearing slider at ultra-low flying heights.
However, shrinking the air bearing gap and operating the slider at ultra-low flying heights has become a source of intermittent contact between the transducing head and the disc. Furthermore, when a disc drive is subjected to a mechanical shock of sufficient amplitude, the slider may overcome the biasing preload force of the load beam assembly and further lift away from or off the disc. Damage to the disc may occur when the slider returns to the disc and impacts the disc under the biasing force of the load beam. Such contact can result in catastrophic head-disc interface failure. Damage to the disc may include lost or corrupted data or, in a fatal disc crash, render the disc drive inoperable. Contact resulting in catastrophic failure is more likely to occur in ultra-low flying height systems. Additionally, intermittent contact induces vibrations detrimental to the reading and writing capabilities of the transducing head.
For the disc drive to function properly, the slider must maintain the proper fly height and provide adequate contact stiffness to assure that the slider does not contact the disc during operation. Also, the air bearing slider must have enhanced take-off performance at start up to limit contact between the slider and the disc. Such contact would cause damage to the slider during take-off and landing of the slider.
Air bearing sliders typically possess three primary degrees of movement, which are vertical motion, pitch, and roll rotation. The movement is relative to the gimbal and load beam associated with three applied forces upon the slider defined as pre-load, suction, and lift force. Steady state fly attitude for the slider is achieved when the three applied forces balance each other. A typical air bearing slider has a taper or step at its leading edge to provide for fast pressure buildup during takeoff of the slider from a resting position to a flying altitude above the disc. Air bearing sliders have a trailing edge at which thin film transducers are deposited. Typically, the air bearing surface includes longitudinal rails or pads extending from the leading edge taper toward the trailing edge. The rail design determines the pressure generated by the slider. The pressure distribution underneath the slider determines the flying characteristics, including flying height and pitch and roll of the slider relative to a rotating magnetic disc. Other characteristics that are affected by the configuration of the air bearing surface of a slider are takeoff velocity, air bearing stiffness, and track seek performance.
Flying height is one of the most critical parameters of magnetic recording. As the average flying height of the slider decreases, the transducer achieves greater resolution between the individual data bit locations on the disc. Therefore, it is desirable to have the transducers fly as close to the disc as possible. Flying height is preferably uniform regardless of variable flying conditions, such as tangential velocity variation from inside to outside tracks, lateral slider movement during seek operations, and air bearing skew angles.
The amount of lift of a slider having parallel rails depends upon relative speed of the slider to the rotating magnetic disc. Normally, the amount of lift increases as the relative speed increases. With movement in a circular pattern, the outside rail of the slider necessarily travels at a higher speed relative to the disc than the inside rail of the slider.
This invention provides control of pressurization and/or suction force formation in air bearing sliders so that the slider flies with controlled roll. An asymmetric taper is disposed on the edge(s) of a slider. The asymmetric taper helps accommodate for the speed differential across the disc radial direction, thereby improving take-off performance, reducing sensitivity to skew angle and altitude variation, and reducing the severity of impacts during ramp loading and unloading.
In one aspect, a leading taper intersecting a leading surface and air bearing surface of the slider is asymmetric about a longitudinal, bisecting plane of the slider. In another aspect, a side taper intersecting a side surface and air bearing surface of the slider is asymmetric about a latitudinal, bisecting plane of the slider. In a third aspect, a rail taper intersecting a rail recess surface and air bearing surface of the slider is asymmetric about a longitudinal, rail-bisecting plane.
The asymmetric taper can be disposed so as to provide increased pressurization on the side of the slider with the lowest air flow velocity (e.g. the inner rail) for faster take off and increased stability of the air bearing. Alternatively, the increased pressurization can be directed toward the outer rail in ramp load / unload operation such that contact between the slider and the disc is avoided or reduced.